WeakHandler:避免內存泄漏的Handler
使用方法:
WeakHandler addSubmitHandler = new WeakHandler(new Handler.Callback() {
@Override
public boolean handleMessage(Message msg) {
...
return false;
}
});
代碼如下：
package com.badoo.mobile.util;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.annotation.VisibleForTesting;
import java.lang.ref.WeakReference;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* Memory safer implementation of android.os.Handler
* <p/>
* Original implementation of Handlers always keeps hard reference to handler in queue of execution.
* If you create anonymous handler and post delayed message into it, it will keep all parent class
* for that time in memory even if it could be cleaned.
* <p/>
* This implementation is trickier, it will keep WeakReferences to runnables and messages,
* and GC could collect them once WeakHandler instance is not referenced any more
* <p/>
*
* @see android.os.Handler
*
* Created by Dmytro Voronkevych on 17/06/2014.
*/
@SuppressWarnings("unused")
public class WeakHandler {
private final Handler.Callback mCallback; // hard reference to Callback. We need to keep callback in memory
private final ExecHandler mExec;
private Lock mLock = new ReentrantLock();
@SuppressWarnings("ConstantConditions")
@VisibleForTesting
final ChainedRef mRunnables = new ChainedRef(mLock, null);
/**
* Default constructor associates this handler with the {@link Looper} for the
* current thread.
*
* If this thread does not have a looper, this handler won't be able to receive messages
* so an exception is thrown.
*/
public WeakHandler() {
mCallback = null;
mExec = new ExecHandler();
}
/**
* Constructor associates this handler with the {@link Looper} for the
* current thread and takes a callback interface in which you can handle
* messages.
*
* If this thread does not have a looper, this handler won't be able to receive messages
* so an exception is thrown.
*
* @param callback The callback interface in which to handle messages, or null.
*/
public WeakHandler(@Nullable Handler.Callback callback) {
mCallback = callback; // Hard referencing body
mExec = new ExecHandler(new WeakReference<>(callback)); // Weak referencing inside ExecHandler
}
/**
* Use the provided {@link Looper} instead of the default one.
*
* @param looper The looper, must not be null.
*/
public WeakHandler(@NonNull Looper looper) {
mCallback = null;
mExec = new ExecHandler(looper);
}
/**
* Use the provided {@link Looper} instead of the default one and take a callback
* interface in which to handle messages.
*
* @param looper The looper, must not be null.
* @param callback The callback interface in which to handle messages, or null.
*/
public WeakHandler(@NonNull Looper looper, @NonNull Handler.Callback callback) {
mCallback = callback;
mExec = new ExecHandler(looper, new WeakReference<>(callback));
}
/**
* Causes the Runnable r to be added to the message queue.
* The runnable will be run on the thread to which this handler is
* attached.
*
* @param r The Runnable that will be executed.
*
* @return Returns true if the Runnable was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting.
*/
public final boolean post(@NonNull Runnable r) {
return mExec.post(wrapRunnable(r));
}
/**
* Causes the Runnable r to be added to the message queue, to be run
* at a specific time given by <var>uptimeMillis</var>.
* <b>The time-base is {@link android.os.SystemClock#uptimeMillis}.</b>
* The runnable will be run on the thread to which this handler is attached.
*
* @param r The Runnable that will be executed.
* @param uptimeMillis The absolute time at which the callback should run,
* using the {@link android.os.SystemClock#uptimeMillis} time-base.
*
* @return Returns true if the Runnable was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting. Note that a
* result of true does not mean the Runnable will be processed -- if
* the looper is quit before the delivery time of the message
* occurs then the message will be dropped.
*/
public final boolean postAtTime(@NonNull Runnable r, long uptimeMillis) {
return mExec.postAtTime(wrapRunnable(r), uptimeMillis);
}
/**
* Causes the Runnable r to be added to the message queue, to be run
* at a specific time given by <var>uptimeMillis</var>.
* <b>The time-base is {@link android.os.SystemClock#uptimeMillis}.</b>
* The runnable will be run on the thread to which this handler is attached.
*
* @param r The Runnable that will be executed.
* @param uptimeMillis The absolute time at which the callback should run,
* using the {@link android.os.SystemClock#uptimeMillis} time-base.
*
* @return Returns true if the Runnable was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting. Note that a
* result of true does not mean the Runnable will be processed -- if
* the looper is quit before the delivery time of the message
* occurs then the message will be dropped.
*
* @see android.os.SystemClock#uptimeMillis
*/
public final boolean postAtTime(Runnable r, Object token, long uptimeMillis) {
return mExec.postAtTime(wrapRunnable(r), token, uptimeMillis);
}
/**
* Causes the Runnable r to be added to the message queue, to be run
* after the specified amount of time elapses.
* The runnable will be run on the thread to which this handler
* is attached.
*
* @param r The Runnable that will be executed.
* @param delayMillis The delay (in milliseconds) until the Runnable
* will be executed.
*
* @return Returns true if the Runnable was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting. Note that a
* result of true does not mean the Runnable will be processed --
* if the looper is quit before the delivery time of the message
* occurs then the message will be dropped.
*/
public final boolean postDelayed(Runnable r, long delayMillis) {
return mExec.postDelayed(wrapRunnable(r), delayMillis);
}
/**
* Posts a message to an object that implements Runnable.
* Causes the Runnable r to executed on the next iteration through the
* message queue. The runnable will be run on the thread to which this
* handler is attached.
* <b>This method is only for use in very special circumstances -- it
* can easily starve the message queue, cause ordering problems, or have
* other unexpected side-effects.</b>
*
* @param r The Runnable that will be executed.
*
* @return Returns true if the message was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting.
*/
public final boolean postAtFrontOfQueue(Runnable r) {
return mExec.postAtFrontOfQueue(wrapRunnable(r));
}
/**
* Remove any pending posts of Runnable r that are in the message queue.
*/
public final void removeCallbacks(Runnable r) {
final WeakRunnable runnable = mRunnables.remove(r);
if (runnable != null) {
mExec.removeCallbacks(runnable);
}
}
/**
* Remove any pending posts of Runnable <var>r</var> with Object
* <var>token</var> that are in the message queue. If <var>token</var> is null,
* all callbacks will be removed.
*/
public final void removeCallbacks(Runnable r, Object token) {
final WeakRunnable runnable = mRunnables.remove(r);
if (runnable != null) {
mExec.removeCallbacks(runnable, token);
}
}
/**
* Pushes a message onto the end of the message queue after all pending messages
* before the current time. It will be received in callback,
* in the thread attached to this handler.
*
* @return Returns true if the message was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting.
*/
public final boolean sendMessage(Message msg) {
return mExec.sendMessage(msg);
}
/**
* Sends a Message containing only the what value.
*
* @return Returns true if the message was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting.
*/
public final boolean sendEmptyMessage(int what) {
return mExec.sendEmptyMessage(what);
}
/**
* Sends a Message containing only the what value, to be delivered
* after the specified amount of time elapses.
* @see #sendMessageDelayed(android.os.Message, long)
*
* @return Returns true if the message was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting.
*/
public final boolean sendEmptyMessageDelayed(int what, long delayMillis) {
return mExec.sendEmptyMessageDelayed(what, delayMillis);
}
/**
* Sends a Message containing only the what value, to be delivered
* at a specific time.
* @see #sendMessageAtTime(android.os.Message, long)
*
* @return Returns true if the message was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting.
*/
public final boolean sendEmptyMessageAtTime(int what, long uptimeMillis) {
return mExec.sendEmptyMessageAtTime(what, uptimeMillis);
}
/**
* Enqueue a message into the message queue after all pending messages
* before (current time + delayMillis). You will receive it in
* callback, in the thread attached to this handler.
*
* @return Returns true if the message was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting. Note that a
* result of true does not mean the message will be processed -- if
* the looper is quit before the delivery time of the message
* occurs then the message will be dropped.
*/
public final boolean sendMessageDelayed(Message msg, long delayMillis) {
return mExec.sendMessageDelayed(msg, delayMillis);
}
/**
* Enqueue a message into the message queue after all pending messages
* before the absolute time (in milliseconds) <var>uptimeMillis</var>.
* <b>The time-base is {@link android.os.SystemClock#uptimeMillis}.</b>
* You will receive it in callback, in the thread attached
* to this handler.
*
* @param uptimeMillis The absolute time at which the message should be
* delivered, using the
* {@link android.os.SystemClock#uptimeMillis} time-base.
*
* @return Returns true if the message was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting. Note that a
* result of true does not mean the message will be processed -- if
* the looper is quit before the delivery time of the message
* occurs then the message will be dropped.
*/
public boolean sendMessageAtTime(Message msg, long uptimeMillis) {
return mExec.sendMessageAtTime(msg, uptimeMillis);
}
/**
* Enqueue a message at the front of the message queue, to be processed on
* the next iteration of the message loop. You will receive it in
* callback, in the thread attached to this handler.
* <b>This method is only for use in very special circumstances -- it
* can easily starve the message queue, cause ordering problems, or have
* other unexpected side-effects.</b>
*
* @return Returns true if the message was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting.
*/
public final boolean sendMessageAtFrontOfQueue(Message msg) {
return mExec.sendMessageAtFrontOfQueue(msg);
}
/**
* Remove any pending posts of messages with code 'what' that are in the
* message queue.
*/
public final void removeMessages(int what) {
mExec.removeMessages(what);
}
/**
* Remove any pending posts of messages with code 'what' and whose obj is
* 'object' that are in the message queue. If <var>object</var> is null,
* all messages will be removed.
*/
public final void removeMessages(int what, Object object) {
mExec.removeMessages(what, object);
}
/**
* Remove any pending posts of callbacks and sent messages whose
* <var>obj</var> is <var>token</var>. If <var>token</var> is null,
* all callbacks and messages will be removed.
*/
public final void removeCallbacksAndMessages(Object token) {
mExec.removeCallbacksAndMessages(token);
}
/**
* Check if there are any pending posts of messages with code 'what' in
* the message queue.
*/
public final boolean hasMessages(int what) {
return mExec.hasMessages(what);
}
/**
* Check if there are any pending posts of messages with code 'what' and
* whose obj is 'object' in the message queue.
*/
public final boolean hasMessages(int what, Object object) {
return mExec.hasMessages(what, object);
}
public final Looper getLooper() {
return mExec.getLooper();
}
private WeakRunnable wrapRunnable(@NonNull Runnable r) {
//noinspection ConstantConditions
if (r == null) {
throw new NullPointerException("Runnable can't be null");
}
final ChainedRef hardRef = new ChainedRef(mLock, r);
mRunnables.insertAfter(hardRef);
return hardRef.wrapper;
}
private static class ExecHandler extends Handler {
private final WeakReference<Handler.Callback> mCallback;
ExecHandler() {
mCallback = null;
}
ExecHandler(WeakReference<Handler.Callback> callback) {
mCallback = callback;
}
ExecHandler(Looper looper) {
super(looper);
mCallback = null;
}
ExecHandler(Looper looper, WeakReference<Handler.Callback> callback) {
super(looper);
mCallback = callback;
}
@Override
public void handleMessage(@NonNull Message msg) {
if (mCallback == null) {
return;
}
final Handler.Callback callback = mCallback.get();
if (callback == null) { // Already disposed
return;
}
callback.handleMessage(msg);
}
}
static class WeakRunnable implements Runnable {
private final WeakReference<Runnable> mDelegate;
private final WeakReference<ChainedRef> mReference;
WeakRunnable(WeakReference<Runnable> delegate, WeakReference<ChainedRef> reference) {
mDelegate = delegate;
mReference = reference;
}
@Override
public void run() {
final Runnable delegate = mDelegate.get();
final ChainedRef reference = mReference.get();
if (reference != null) {
reference.remove();
}
if (delegate != null) {
delegate.run();
}
}
}
static class ChainedRef {
@Nullable
ChainedRef next;
@Nullable
ChainedRef prev;
@NonNull
final Runnable runnable;
@NonNull
final WeakRunnable wrapper;
@NonNull
Lock lock;
public ChainedRef(@NonNull Lock lock, @NonNull Runnable r) {
this.runnable = r;
this.lock = lock;
this.wrapper = new WeakRunnable(new WeakReference<>(r), new WeakReference<>(this));
}
public WeakRunnable remove() {
lock.lock();
try {
if (prev != null) {
prev.next = next;
}
if (next != null) {
next.prev = prev;
}
prev = null;
next = null;
} finally {
lock.unlock();
}
return wrapper;
}
public void insertAfter(@NonNull ChainedRef candidate) {
lock.lock();
try {
if (this.next != null) {
this.next.prev = candidate;
}
candidate.next = this.next;
this.next = candidate;
candidate.prev = this;
} finally {
lock.unlock();
}
}
@Nullable
public WeakRunnable remove(Runnable obj) {
lock.lock();
try {
ChainedRef curr = this.next; // Skipping head
while (curr != null) {
if (curr.runnable == obj) { // We do comparison exactly how Handler does inside
return curr.remove();
}
curr = curr.next;
}
} finally {
lock.unlock();
}
return null;
}
}
}
